[PATCH v2] KVM: arm64: Take the SRCU lock for page table walks in fault injection and AT emulation

[Hyunwoo Kim <imv4bel@gmail.com>]

walk_s1() and kvm_walk_nested_s2() expect to be called while holding
kvm->srcu to guard against memslot changes. While this is generally
the case, __kvm_at_s12() and __kvm_find_s1_desc_level() call into the
respective walkers without taking kvm->srcu.

Fix by acquiring kvm->srcu prior to the table walk in both instances.

Cc: stable@vger.kernel.org
Fixes: 50f77dc87f13 ("KVM: arm64: Populate level on S1PTW SEA injection")
Fixes: be04cebf3e78 ("KVM: arm64: nv: Add emulation of AT S12E{0,1}{R,W}")
Suggested-by: Oliver Upton <oupton@kernel.org>
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
---
Changes in v2:
- Wrap only the walker calls with scoped_guard() and move the injection
  lock into __kvm_find_s1_desc_level(), as suggested by Oliver.
- Reword the commit message as suggested.
- v1: https://lore.kernel.org/all/ah7_BAAzHggzdZeI@v4bel/
---
 arch/arm64/kvm/at.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/at.c b/arch/arm64/kvm/at.c
index 9f8f0ae8e86e..889c2c15d7bd 100644
--- a/arch/arm64/kvm/at.c
+++ b/arch/arm64/kvm/at.c
@@ -1569,7 +1569,8 @@ int __kvm_at_s12(struct kvm_vcpu *vcpu, u32 op, u64 vaddr)
 	/* Do the stage-2 translation */
 	ipa = (par & GENMASK_ULL(47, 12)) | (vaddr & GENMASK_ULL(11, 0));
 	out.esr = 0;
-	ret = kvm_walk_nested_s2(vcpu, ipa, &out);
+	scoped_guard(srcu, &vcpu->kvm->srcu)
+		ret = kvm_walk_nested_s2(vcpu, ipa, &out);
 	if (ret < 0)
 		return ret;
 
@@ -1665,7 +1666,8 @@ int __kvm_find_s1_desc_level(struct kvm_vcpu *vcpu, u64 va, u64 ipa, int *level)
 	}
 
 	/* Walk the guest's PT, looking for a match along the way */
-	ret = walk_s1(vcpu, &wi, &wr, va);
+	scoped_guard(srcu, &vcpu->kvm->srcu)
+		ret = walk_s1(vcpu, &wi, &wr, va);
 	switch (ret) {
 	case -EINTR:
 		/* We interrupted the walk on a match, return the level */
-- 
2.43.0